#include <stdio.h>
#include <queue>

using namespace std;

unsigned int i,n,t;

int main()
{	scanf("%d", &n);
	std::priority_queue<unsigned int> q;
	for (i=1;i<=n/2+1;i++)
	{	scanf("%d", &t);
		q.push(t);
	}
	while (i<=n)
	{	scanf("%d", &t);
		q.push(t);
		q.pop();
		i++;
	}
	if (n%2==1)
		printf("%d.0\n", q.top());
	else
	{	n=q.top();q.pop();t=q.top();
		double a=(double(n+t))/2;
		printf("%.1f\n", a);
	}
	return 0;
}
